Practice MCQ Questions and answers on Physics-GK

The density of dry air is more than that of moist air (when moisture is removed from air, its density increases). The speed of sound in a medium is inversely proportional to the square root of its density. Therefore, the speed of sound in moist air is more than that in dry air.

Air pressure has almost no effect on sound speed. It has no effect at all in an ideal gas approximation, because pressure and density both contribute to sound velocity equally, and in an ideal gas the two effects cancel out. In an ideal gas, intermolecular gaps are always taken to be very large, regardless of pressure.

Air pressure has no effect at all in an ideal gas approximation. This is because pressure and density both contribute to sound velocity equally, and in an ideal gas the two effects cancel out, leaving only the effect of temperature. Sound usually travels more slowly with greater altitude, due to reduced temperature.

An adiabatic process is one that occurs without transfer of heat or matter between a thermodynamic system and its surroundings. In an adiabatic process, energy is transferred only as work.
Rarefaction is the reduction of an item’s density, the opposite of compression.

When two similar sources vibrate with slightly different frequencies, a regular rise and fall occurs in the loudness of tone. This phenomenon is known as beats.

Pressure is related to the number of particles of the medium in a given volume. More density of the particles in the medium gives more pressure and vice-versa. Thus, propagation of sound may be visualised as propagation of pressure variations or density variations in the medium.

In commercial areas, it is 65 dB and 55 dB while in residential areas it is 55 dB and 45 dB during daytime and night respectively.

Frequency = velocity/wavelength = 500/4 = 125 Time period = 1/Frequency = 1/125 = 0.008

Sound waves cannot travel in the vacuum of space because there is no medium to transmit these mechanical waves. Classical waves transfer energy without transporting matter through the medium.

Sonar (originally an acronym for Sound Navigation And Ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels.